LED plate driver failure – 24W round plate

This article documents failure of a 24W LED oyster. The luminaire was purchased complete on eBay for about $45.

After about two years use, the light became sensitive to switching transients on the mains, visibly blinking when other appliances were turn off or on. After some time, this progressed to oscillating on and off for a few seconds on a cold startup, but on hot startup it was stable.

Because of the nature of the fault, the driver board was swapped as a first step, and it cured the problem.

The symptoms hints a capacitor failure, and ESR of both electrolytic caps on the board were measured. The large cap at left (6.8µF 400V) had ESR=109Ω, a good one should be of the order of 1Ω, so this is the faulty part.

This is a key problem with LED luminairs, here a $49 plus fitting investment ($100) would be rendered worthless for most users by a low quality $0.02 part.

Whilst I did not intend repairing the failed module, I am inclined to buy a quality cap and fit it, and return the repaired unit to spares stock, it might last longer than the Chinese replacements.

Update 21/10/2022

Well I purchased some cheap Chinese caps, 20 for $2.90 incl shipping.

In fact I bought twice, the first were not delivered in 75 days so I claimed a refund. This is a common Aliexpress scam, goods were probably not shipped which means they get the money unless I follow up and claim. After some months, I have new caps which test good.

The large electrolytic on the driver board is the most common failure in my experience.

The equivalent series resistance of the failed cap was unstable at around 80Ω, should be less than 10Ω.

Above, the reworked driver. The new cap is the larger one lying on its side.

It was fitted to the luminaire to test it so positively determine that it works reliably after the replacement, that indeed the cap was the problem.

It has been working for some days now, it is only a matter of time before it fails again… weeks or years.


I have studied failure of LED lighting over 10 years or so, and just like the Compact Fluorescent Lights before them, they just do not live up to claims of life, efficiency, cost effectiveness. Post mortem analysis informs that conclusion.